Liquid Crystal Display (LCD) panels are now in widespread use, such as LCD TV, cell phones, digital cameras, etc. Liquid crystals are unable to emit lights that need a backlight unit to provide lights for LCD panels. The backlight unit can be separated into the Direct-Type backlight unit and the Side-Edge Type backlight unit. Currently the direct-type backlight unit is a main stream because of advantages with high-efficiency and less assembly parts.
Referring to FIG. 1, a structural drawing of a conventional direct-type backlight unit structure is illustrated. The conventional direct-type backlight unit structure at least comprises a plurality of light generation components 11, a light emitting surface 12, and at least one reflection surface 13. The light generation component 11 is used to generate lights and the light generation component 11 can be a Light Emitting Diode (LED) or a Cold Cathode Fluorescent Lamp (CCFL). In general, LED is current trend. In addition, the light emitting surface 12 is usually set on the light generation component 11. The light generated from the light generation component 11 can pass through the light emitting surface 12 for producing a uniform backlight. The light generation component 11 usually generates the light without specific directions that proceeds everywhere. Therefore, the reflection surface 13 is set in the side of the backlight unit. The light proceeds to the backlight unit that is then reflected by the reflection surface 13 for mixing in a mixed space 14. The mixing efficiency will be better when the height of the mixed space 14 is higher that can generate a uniform backlight. The design in the direct-type backlight unit structure is required to be a thin type as lowering the height of the light generation component 11. In another word, the mixing efficiency in the direct-type backlight unit will be sacrificed. Furthermore, the light generation component has been improved to generate a light with higher brightness that decreases the amount of the light generation component to achieve the same brightness. Consequently, the mixing efficiency is worse to generate a backlight without well mixed.
Referring to FIG. 2, a structural drawing of another conventional direct-type backlight unit structure is illustrated. The conventional direct-type backlight unit structure at least comprises a plurality of light generation components 21, a light emitting surface 12, and at least one reflection surface 13. The light generation component 21 can be a Side Emitting LED that comprises a lens 211 to take the light (especially in an upward light) generated from the light generation component 21 that utilizes reflecting or refracting to toward two sides for emitting, as shown in a dotted line 212. The light is reflected by the reflection surface 13 while proceeding to the side of the backlight unit and the reflected light is then mixed in a mixed space 22 that passes through the light emitting surface 12 to generate a uniform backlight. Above direct-type backlight unit structure uses the mixed space 22 with the lower height to achieve well mixed. However, the price for the light generation component 21 is expensive that increases the cost of the conventional direct-type backlight unit structure.
Referring to FIG. 3, a structural drawing of third conventional direct-type backlight unit structure is illustrated. The third conventional direct-type backlight unit structure at least comprises a plurality of light generation components 31, a plurality of reflection plates 32, and a light guide plate 33. The light generation component 31 can be a LED with high brightness that is used to generate a light (including the upward light). The reflection plate 32 is used to reflect the upward light that takes the reflected upward light to enter the light guide plate from the side 331 of the light guide plate 33. The light guide plate 33 is used to guide the direction of the light that takes the liner light to scatter to be a uniform area light in order to generate a uniform backlight from the top. The third conventional direct-type backlight unit structure further comprises at least one reflection surface 13 that is used to reflect the scattering light to back to the light guide plate in order to avoid fleeing and improve efficiency. However, the third conventional direct-type backlight unit structure needs the light guide plate 33 that increases the weight and the light guide plate 33 absorbs a part of the light that decreases the efficiency. Above disadvantages must be resolved by providing a direct-type backlight unit structure having a reflection mirror.